For manufacturing semiconductor devices, fine processing utilizing a photolithographic technique has been conventionally used. In the fine processing, forming a thin film of a photoresist composition on a substrate to be processed such as a silicon wafer; irradiating the substrate with active light such as ultraviolet through a mask pattern having a pattern of semiconductor device; developing the substrate; and treating the substrate to be processed such as a silicon wafer by etching with an obtained photoresist pattern as a protection film.
In recent years, semiconductor devices tend to be highly integrated, and a wavelength of active light to be used becomes shorter, such that from KrF excimer lasers (248 nm) to ArF excimer lasers (193 nm). Accordingly, the active light produces diffused reflections and standing waves from a substrate. To overcome such disadvantages, an anti-reflective coating (Bottom Anti-Reflective Coating, BARC) has been applied between a photoresist and a substrate to be processed as a resist underlayer film so as to prevent reflection. As the anti-reflective coating, inorganic anti-reflective coatings containing titanium, titanium dioxide, titanium nitride, chromium oxide, carbon, α-silicon, or other compounds; and organic anti-reflective coatings containing light-absorbing substances and macro molecule compounds have been known. For forming films, the former requires vacuum deposition devices, CVD devices, sputtering devices, or the like, the latter requires no special devices. Such an advantage leads to a large number of studies on the organic anti-reflective coating. Examples of the organic anti-reflective coatings include an acrylic resin anti-reflective coating having a hydroxy group that is a cross-linking reaction group, and a light-absorbing group in one molecule; and a novolac resin anti-reflective coating having a hydroxy group that is a cross-linking reaction group, and a light-absorbing group in one molecule.
As physical properties desired for organic anti-reflective coatings are described as follows: large absorbance to light and radiation; no intermixing with photoresist layers (insoluble in resist solvents); no low molecular weight materials being diffused from anti-reflective coating materials to the top coating resist at the time of application, or heating and drying; and a dry etching rate larger than that of a photoresist (see Patent Document 1).
In recent years, an ArF liquid immersion lithography technique in which exposure is conducted through water has been extensively investigated as a next-generation photolithographic technique that follows photolithographic techniques using ArF excimer lasers (193 nm). However, photolithographic techniques utilizing light are facing their limits, and an EUV lithography technique utilizing EUV (having a wavelength of 13.5 nm) has been gathering attention as a novel lithography technique, which follows the ArF liquid immersion lithography technique.
In a device production process utilizing the EUV lithography, defective conditions are caused by adverse effects resulting from ground substrates and/or EUV, for example, a shape of a resist pattern for the EUV lithography becomes a flare or an undercut, and thus a good, straight-shaped resist pattern cannot be obtained; and a sensitivity to EUV is too low to obtain sufficient throughput. Accordingly, in steps of the EUV lithography, although resist underlayer films (anti-reflective coatings) having anti-reflectivity are not needed, resist underlayer films for EUV lithography that can reduce such adverse effects to form a good, straight-shaped resist pattern and to increase a resist sensitivity are needed.
After resist underlayer films for EUV lithography are formed, resists are applied on the films. As in the case of anti-reflective coatings, essential properties of the resist underlayer films are thus as follows: causing no intermixing with resist layers (insoluble in resist solvents); and no low molecular weight materials being diffused from anti-reflective coating materials to the top coating resist at the time of application, or heating and drying.
In the generation in which EUV lithography is used, resist patterns are extremely fine and a thinner resist for EUV lithography are desired. Therefore, the time required for a removing step of organic anti-reflective coating by etching needs to be greatly shortened, and resist underlayer films for EUV lithography available as thin films or resist underlayer films for EUV lithography having a large selection ratio of an etching rate with respect to a resist for EUV lithography.
Examples of the resist underlayer film for EUV lithography include resist underlayer film-forming compositions containing a novolac resin having halogen atom(s), or a resin having acid anhydride(s) (see Patent Documents 2 and 3).